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Questions tagged [natural-join]

A natural join is a relational operation that joins on the like-named attributes between tables

Natural join (⋈) is a binary operator that is written as (R⋈S) where R and S are relations. The result of the operation is the set of all combinations of tuples in R and S that have equal values on their common attribute names. The resulting relation has a heading consisting of the set-union of the attributes from R and S, i.e. there are no duplicate attribute names in the result.

If the joined relations have no attribute names in common then R⋈S is equivalent to R×S (Cartesian product).

The natural join of any relation, R, to itself is R (R⋈R = R).

The ISO Standard SQL syntax for natural join (R⋈S) is:

SELECT * FROM R NATURAL JOIN S;
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Two models in one view (Single view) using php MVC

I have two tables USERS and join_class, according to MCV each table has its own Model which means i have two models ... USER MODEL and JOIN_CLASS MODEL. How can i use two model in a single view. JOIN_CLASS TABLE id user_id class_id 2 19 …
Sizwe
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Is there a way to make a "natural join" with a table having a foreign key on another table?

This is just a dummy example. In reality I have a foreign key which references a lot of more columns. That why I'm trying replace the normal join with a "natural join" I have a table which has a foreign key on another table. The columns don't have…
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Using WHERE clause on NATURAL JOIN

I am studying the book Database System Concepts 6th ed. which uses the example of a university database. The schema of this database is as follows. The bold represent the primary keys: department(dept_name, building, budget) course(course_id,…
ginos
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SQL query to join these 3 tables to remove spurious rows - OWNER, TYPE, PERSON

I'm having some trouble joining these 3 tables. Table1 OWNER TYPE O1 T1 O1 T2 O2 T1 Table2 OWNER PERSON O1 P1 O1 P2 O2 P1 Table3 TYPE PERSON T1 P1 T2 P2 T1 P2 I want to do a…
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Relational Algebra: Natural Join having the same result as Cartesian product

I am trying to understand what will be the result of performing a natural join between two relations R and S, where they have no common attributes. By following the below definition, I thought the answer might be an empty set: Natural Join…
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Understanding Natural Join in SQL

So I am fairly new to SQL and currently I am stuck with the concept of Natural Join. Currently I understand that the Natural Join operator joins tables by matching all columns with the same names and discarding duplicate columns and discarding rows…
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Natural join works but not with all values

I can't understand whats happening... I use two sql queries which do not return the same thing... this one : SELECT * FROM table1 t1 JOIN table1 t2 on t1.attribute1 = t2.attribute1 I get 10 rows this other : SELECT * FROM table1 NATURAL JOIN…
Maximilien Faure
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Comparing nulls during join

I read that null cannot be compared with null and the result is always false. In the below link I am able to compare 2 nulls and the rows are returned. CREATE TABLE user (id varchar(50), banstatus varchar(100)); INSERT INTO user (id, banstatus)…
Zephyr
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PostgreSQL Natural Join is not working for two related tables

I've got the following design of the two tables that I am having trouble joining using NATURAL JOIN to test the referential integrity. It works with INNER JOIN, however it doesn't with NATURAL JOIN : Table 1. Project DROP TABLE IF EXISTS…
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LARAVEL MYSQL how to use natural JOIN

I need a return in collection to paginate but i can only a return in array because the query use a natural JOIN. How could I do this query using Laravel collections : SELECT mensagens.* FROM mensagens NATURAL JOIN ( SELECT id_emissor,…
Gilberto S. Rocha
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Natural join of 3 tables in mysql

So i have 3 tables, movies(contains columns id and name), directors(id, first_name, last_name) and movies_directors(movie_id and director_id). I want to combine these 3 tables, since they have same values(director_id and movie_id) and then project…
user6417385
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NATURAL FULL OUTER JOIN or USING, if common attribute is NULL

So if table A is: no | username 1 | admin 2 | chicken And table B is: id | no a | 1 b | 3 c | 4 Then, I do a NATURAL FULL OUTER JOIN as so: SELECT no FROM A NATURAL FULL OUTER JOIN B; Then, what is the result? And is the result the…
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Join two select statements sql

I have two sql statements that I wish to join via natural join but for some reason the following is giving me an error: (select city_name from city left join country on country.country_name=city.country_name where country.continent='Europe' and…
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ORACLE Natural Join returns empty results "no rows selected" have same columns both tables

HELLO my main goal is to take x tables and join them w/o getting duplicates Columns which is used to detect the rows for the join operation. So i found that natural join is what i have looking for : NOT wanted result with inner join…
Stav Bodik
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Not sure im doing sql queries correctly

department(dept_name, building, budget) course(course_id, title, dept_name, credits) instructor(ID, name, dept_name, salary) section(course_id, sec_id, semester, year, building, room_number, time_slot_id) teaches(ID, course_id, sec_id, semester,…
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